Radio Receiving for Beginners, Rhey T. Snodgrass and Victor F. Camp, 1922, pages 5-6:

HOW  CAN  I  RECEIVE  RADIO?
 
frontispiece     THIS question is on the lips of thousands, perhaps millions, of people. It may be answered in so many ways as to leave one in a hopeless state of bewilderment, for this very new and very fascinating science is most uncanny in its ramifications even at the present time, to say nothing of its almost daily advancement and future possibilities.
    On the other hand, your question may be answered quite simply; in a manner which will enable you to begin receiving at once, and to understand the fundamental principles of radio. From that point you may advance as you have time, inclination and means to go into more expensive apparatus.
    Radio, particularly radio telephony, is too new to have become "standardized" beyond the elementary operations. On the more advanced questions you will find almost as many opinions you find expert operators, and you will find good books galore on every phase of the subject.
    The present little volume will leave the more technical and diversified possibilities of radio receiving to be pursued in more exhaustive books, and keep down to the simple answer to your simple question, "How can I receive radio?"
    We must necessarily choose between various methods. In so doing it is not claimed that ours is the ONLY way. Whether ours is the BEST way might open up a never ending argument, but the methods laid down in this book are known to be good, practical, easy to understand, simple to follow, and elastic enough to meet your allowance of time, study and cash outlay.
    In the following text you will find reference to some instruments with which you may not be familiar. All of the instruments covered by this book will be found fully described in Chapter IX.
    We believe this plan is better than to fill the text with interruptive explanations, as some of our readers may not require all of them.
Pages 7-8:
CONTENTS
CHAPTER
I.  INTRODUCTION.
 Elementary--no previous knowledge of electricity or radio required--popular demand for simple practical instruction--easy to start-- simple apparatus will do--range of cost--how to begin receiving at once--no license required for receiving--may purchase complete outfit or separate instruments--same outfit receives both telephone and telegraph signals--telephone easier and more entertaining--broadcasting music, lectures, news, market reports, sports, interviews, church services--important developments by amateurs--open field for experiment--advise start with simple set and build up with experience.
VIII.  GENERAL  HINTS.
  Little things to look out for--results of practical experience--telegraph code.
Pages 11-15:
RADIO  RECEIVING


I


INTRODUCTION


    WE assume that you have no previous knowledge or experience in radio work. You wish to learn how you may begin at once to "listen in" on the astounding things which are passing through the air all the time, day and night, right about our heads at this very moment.
    Radio is a most fascinating pastime. While its possibilities are so boundless and intricate that the most advanced engineers are only beginning to solve them, you may begin with very simple operations which may be explained in simple terms. Thousands of twelve year old boys, and girls, are operating satisfactorily, entertaining their families and friends, while educating themselves. Anyone with common sense can readily grasp the elementary principles and begin receiving at once. After that it is simply a question of time, study and practice. Every step of the way is most alluring--romantic. One has a constant sense of participating in the performance of magic. Nobody starts receiving and abandons it. One step leads to the next, and you simply cannot let it alone. All the while you are playing with one of the most worth-while developments of the age.
    Many of the important steps in the progress of radio have been discovered by amateurs as the result of their own experiments. Indeed, radio may be called the science of the amateur. As this book goes to press there are estimated to be amateur radio stations and residences with receiving outfits in this country to the number of over half a million, and the number is leaping ahead every day. In the United States the laws and restrictions are very favorable to amateurs. This largely accounts for America's outstanding leadership in the development of radio over European countries, where the amateur is too much restricted to develop new ideas and practices. Many an amateur in this country has worked out radio operations and instruments which have led him into a fine professional career. In fact, most of the prominent names in radio are the names of men who began by "playing with radio."
    In the United States, at the present moment, no license is required for receiving radio telephone or telegraph. You may "listen in" to your heart's content, but a license and inspection are required for transmitting either telephone or telegraph. As transmitting is quite a different operation, and one which may be more properly considered after receiving is mastered, the present discussion will be confined to radio receiving, leaving the subject of transmitting to be covered in another volume.
    You can begin receiving with very little outlay and very little study. The same apparatus will be used for receiving both telegraph and telephone signals. As telegraph comes in code (dots and dashes) we may consider that the more interesting and certainly the easier operation will be receiving telephone. At the present writing there are large and powerful sending stations located in so many places that practically every point in the United States is within reasonable amateur hearing distance of at least one of them. From these stations most interesting programs are being broadcasted daily, including music, lectures, news bulletins, weather and market reports, church services, interviews with prominent persons, and other features. Besides these larger stations there are many experimental stations and licensed amateur stations constantly sending out interesting matter; all of which you may easily receive in your own home with a surprising degree of clearness and regularity from the first.
    With most of us the question of cost is, to say the least, a factor. You may enter the radio wonderland on an investment of fifteen or twenty dollars, and get fair results within a limited radius. A little larger investment will give a little wider radius and more dependable results. Some one has said that your apparatus should cost a dollar per mile of effective operation, from fifteen up. This should not be taken too literally as an absolute rule, but is a fair indication of cost.
    If you have time and a little skill you may effect some economy and gain good experience by making some of the instruments yourself, or you may purchase the instruments separately and assemble and connect them; or you may purchase neat cabinets in wide variety with the instruments self-contained and requiring only proper connections to be made, according to instructions furnished. We will not attempt to choose your instruments for you, but if you have not already selected them, this book will assist you in making a wise selection, and still leave you a wide range of option according to your requirements.
    In most of our cities and many villages there is a local amateur radio club. Like everything pertaining to radio, these clubs are growing daily in numbers and usefulness. Many of them are affiliated with the American Radio Relay League, with headquarters at Hartford, Conn., which is an international amateur organization. It will interest you and help keep you abreast of the newest developments to attend the meetings of your local club. The A. R. R. L., moreover, is instrumental in guiding legislation tending to foster amateur practice and to develop a large group of trained amateurs which has already proved to be a great national asset.
Pages 81-88:
VIII


GENERAL  HINTS

    THERE are many little things you can do, and little points you should know about, in order to make your practice of radio more satisfactory. A very large book would hardly contain all of them. But a few which may be easily understood may well be included here.
    The foregoing instructions will, if carefully followed, show you how to master all of the problems ordinarily met during your beginning stage, with the exception of one. That one is "static." It may be termed the general atmospheric electricity, which is abroad all the time in greater or less degree, but not always troublesome. Its most troublesome demonstration is in the form of lightning. During an electric or thunder storm, do not attempt to operate your radio set, and if you have a lightning switch, be sure it stays in the ground position until the disturbance is surely past. At some times static is very bothersome, causing a rattling or grating noise in the phones which makes the signals themselves almost inaudible or breaks into them with very rude interruptions. If you hear noises in your phones and are not sure whether they come from outside or whether they might be caused by some fault within your set, disconnect the instruments from the lead-in, and place the antenna line in contact with the ground. If the noise ceases, it must have been outside, probably static. If it does not cease, or greatly diminish, it is somewhere within the set.
    You will often experience "interference"; that is, the interjection of signals other than those you wish to receive. Careful tuning will eliminate most all ordinary interference from a well-designed receiving set. In general, coupling loosened to the limit, small amount of capacity in the antenna condenser, and balancing with additional inductance, together with other adjustments already described, are your means of tuning out undesirable signals. If you are unfortunate enough to be near a transmitting station whose power and signal strength are many times greater than the more distant signals, for which you are tuned, you are literally "up against" it, until the interference ceases, especially if its wave length is near the one to which you are tuned. Here is your opportunity to experiment and endeavor to find ways to eliminate interference to a greater degree.
    You have noted our references to audio frequency and radio frequency. The term frequency is used in connection with any form of rhythmical motion, denoting the number of movements in a given time. In the case of electrical currents, the unit of time is one second. Audio frequencies are those in which the current makes less than 10,000 movements or cycles per second. Radio frequencies are those above 10,000 cycles per second.
    Sometimes a little greater or less capacity across the phones will slightly improve your signals. A variable condenser is admirably adapted to this use, and will require a corresponding adjustment of the wing variometer. In a cabinet set, however, the phone condenser has probably been worked out to a nicety and had best be left alone.
    In regulating the amount of capacity, or inductance, or current in the A battery, you will at first be amazed at the great difference effected by a very slight adjustment. Some sets are equipped with micrometer adjustments, as the direct action of the hand will often turn the knobs too far.
    Bear in mind the importance of keeping all wires connecting your instruments as short as possible, particularly the wire leading to the grid.
    Avoid parallel wires, as far as you can, as the capacity between them may disturb your adjustments, and if your wires must cross each other, let them do so at right angles and keep them apart.
    A whole book could be written about tight connections. Loose ones cause endless trouble. Unless wires are securely and tightly clamped to their proper connections they should be soldered. Often a wire is properly fastened to a binding post but the post itself is loose in its base, or the wire on the under end of it is not properly screwed or soldered down. Make a habit of placing the end of a wire around a binding post or other screw from left to right, so that tightening the screw will not tend to throw the wire out of place.
    When "skinning" the ends of insulated wire, be sure to get a good bright metal surface on the wire, scraping it if necessary. For the sake of neatness, you may wrap the ends of the insulation with tape to avoid fraying. Some insulation is made of two layers wound in opposite directions, in which case the ends may be tied in a knot and clipped short, so as to prevent further unwinding.
    Pay particular and frequent attention to the terminals of your storage battery. The contacts should be clean and bright. A coat of vaseline will help to keep them so.
    Always be sure your B battery is correctly connected, as a wrong connection may result in turning this high voltage loose where it would burn out a tube or do other damage while also exhausting itself.
    Do not install your radio instruments in the cellar or other damp places. Moisture will surely harm them and impair their efficiency.
    Bear in mind that radio frequency currents are very minute and very sensitive, and must be handled accordingly. Oilcloth acts as a conductor of these minute currents, and should never be used as a cover for your radio table. Use felt, or some sort of cloth, if you wish a cover. Black paint often contains lamp-black which is a conductor and will prevent proper operation of the instruments. Plain wood coated with shellac or varnish is free from this source of trouble.
    Electric light wires or extension cords, when within a few feet of your receiving apparatus, will often induce sufficient current to cause an objectional hum, which you will note in your receivers.
    All movable contacts, such as switch points and contacts on a slide tuner, should be kept clean and bright. If you have a lightning switch, occasionally clean the blade and both sockets, so as to insure a good bright metal contact.
    While some cabinet sets come with sockets to hold tubes in a horizontal position, it is preferable to place tubes in a vertical position on account of a possible sagging of the filament within the tube. See that the contact points at the base of the tube are clean and bright, and that the spring contacts in the socket are clean and in good tension.
    Your A and B batteries will not last indefinitely. You can tell when the A battery is running down, by the diminished glow in your tubes. You can have it re-charged for a small outlay, or if you have alternating current in your house, a small rectifier will enable you to charge it yourself. If your current is direct, you had best consult your local electrician or the makers or agents of the battery, who will advise you how to charge from direct current. Of course, if you use dry cells for A battery, they can be replaced with new ones. The condition of the B battery should be tested from time to time with a small voltmeter. If each block registers a full 22½ volts it is still in condition to use. When it falls appreciably below, it should be replaced with a new block.
    For many purposes, you will find flexible cord preferable to wire for making connections. Common lamp-cord will do. In purchasing, get the kind in which the two cords may be separated by untwisting, as some kinds have a woven cover holding the two cords together. To keep the fine wire ends from getting snarled, and to insure a good connection, remove the insulation for half an inch from the end, clean and twist the fine wires together and solder.
    Test clips, attached to the two ends of flexible cord, are very handy for temporary or changeable connections. The clips themselves are like a "tie clasp," only larger and stronger. Fasten the ends of the flexible cord to the clips by soldering. Keep a dozen or more of these clip-cords on hand, in various lengths.
    If you intend doing anything more than merely buying a set, connecting it, and listening--you should by all means provide yourself with a soldering outfit, and use it freely. Whether of the electric variety or not, you will be surprised to see how easy it is to make fine tight connections. Use soft solder, which comes in small strips. Do not use acid, but use rosin or some form of patent flux such as Solderall or Nokorode.
    By all means learn the telegraph code. It will open up to you a great many interesting things. With a little study you can readily memorize the code and then with practice you can read the telegraph signals as well as the telephone. For practice in listening to the dots and dashes you can get a little buzzer, or make one out of a door bell. Let us emphasize this telegraph business--it will greatly repay you.
    Every licensed radio station has a call signal. The official list is published in book form by the government. One book gives the commercial and government stations, and a separate book lists the amateur stations. Each book is sent post paid for fifteen cents. Write to the Superintendent of Documents, Government Printing Office, Washington, D. C.
    When you begin to think of transmitting telegraph or telephone, and wish to post yourself regarding the method of procuring the necessary license, such information may be had by addressing the Radio Inspector, Bureau of Navigation, Department of Commerce, Washington, D. C., or you may write to the Radio Inspector of your district. The division by districts is shown in the Call Book.